Synergistic microbicidal combinations containing 2-methyl-3-isothiazolone and certain commercial biocides

ABSTRACT

Synergistic microbicidal compositions are disclosed, comprising 2-methyl-3-isothiazolone and one or more of seven known microbicides for more effective, and broader control of microorganisms in various systems.

This application is a division, of application Ser. No. 07/975,260, filed Sep. 4, 1992, now abandoned, which in turn is a continuation of Ser. No. 07/798,398 filed Nov. 26, 1991 now abandoned.

BACKGROUND OF THE INVENTION

A. Field of the Invention

This invention concerns microbicidal compositions which include an isothiazolone and one or more other biocides, and which are intended to provide more effective and broader control of micro-organisms in various industrial systems and for household products, agricultural products, and biomedical products, etc. In particular, the present invention relates to the use of a composition of 2-methyl-isothiazolin-3-one, hereinafter referred to as 2-methyl-3-isothiazolone, with one or more of the following seven compounds: p-chloro-m-xylenol, sodium dichlorophene, bis-(2-hydroxy-5-chlorophenyl) sulfide, benzylbromoacetate, dodecylamine, 4-(2-nitrobutyl)morpholine and dipropylamine ether.

The term "microbicidal" (or "antimicrobial" or "biocidal") as used herein is intended to encompass, but is not restricted to, all bactericidal, fungicidal and algicidal activity.

B. Prior Art

Isothiazolones are described in U.S. Pat. Nos. 3,761,488; 4,105,431; 4,252,694; 4,265,899 and 4,279,762, and elsewhere. Their use as microbicides is well known.

It is the principal object of this invention to provide synergistic compositions which are more efficacious known microbicidal compositions.

SUMMARY OF THE INVENTION

We have found that compositions formed from one or more of the seven specified compounds (supra) unexpectedly afford synergistic antimicrobial activity against a wide range of microorganisms: the disruptive action on the organisms by the two compounds together is unexpectedly greater than the sum of both compounds taken alone. This synergy does not arise from the expected activity of the components nor from the expected improvement in activity. As a result of the synergy, the effective dose required can be lowered, which is not only more economical but also increases safety margins. The synergistic compositions of the present invention provide more effective and broader control of microorganisms in a number of systems.

The present invention thus provides a composition having microbicidal activity which includes 2-methyl-3-isothiazolone and a second component selected from one or more of the group consisting of: p-chloro-m-xylenol, sodium dichlorophene, bis-(2-hydroxy-5-chlorophenyl) sulfide, benzylbromoacetate, dodecylamine,4-(2-nitrobutyl)morpholine and dipropylamine ether wherein the weight ratio of 2-methyl-3-isothiazolone to the second component is from about 40:1 to 1:32.

Important applications of the synergistic antimicrobial compositions of the present invention include but are not limited to: inhibiting the growth of bacteria and fungi in aqueous paints and coatings, adhesives, sealants, latex emulsions, and joint cements; preserving wood; preserving cutting fluids, controlling slime-producing bacteria and fungi in pulp and papermills and cooling towers; as a spray or dip treatment for textiles and leather to prevent mold growth; protecting paint films, especially exterior paints, from attack by fungi which occurs during weathering of the paint film; protecting processing equipment from slime deposits during manufacture of cane and beet sugar; preventing microorganism buildup and deposits in air washer or scrubber systems and in industrial fresh water supply systems; preserving fuel; controlling microorganisms contamination and deposits in oil field drilling fluids and muds, and in secondary petroleum recovery processes; preventing bacterial and fungal growth in paper coatings and coating processes; controlling bacterial and fungal growth and deposits during the manufacture of various specialty boards, e.g., cardboard and particle board; preventing sap stain discoloration on freshly cut wood of various kinds; controlling bacterial and fungal growth in clay and pigment slurries of various types; as a hard surface disinfectant to prevent growth of bacteria and fungi on walls, floors, etc.; as a preservative for cosmetic and toiletry raw materials, floor polishes, fabric softeners, household and industrial cleaners; in swimming pools to prevent algae growth; inhibiting the growth of harmful bacteria, yeasts, fungi on plants, trees, fruits, seeds, or soil; preserving agricultural formulations, electrodeposition systems, diagnostic and reagent products, medical devices; protecting animal dip compositions against the buildup of microorganisms, and in photoprocessing to prevent buildup of microorganisms, and the like.

The compositions of the invention may be added separately to any system or may be formulated as a simple mixture comprising its essential ingredients, and if desired a suitable carrier or solvent, or as an aqueous emulsion or dispersion.

The invention also provides a method of inhibiting or preventing the growth of bacteria, fungi or algae in a locus subject or susceptible to contamination thereby which comprises incorporating into or onto the locus, in an amount effective to inhibit or prevent said growth, any of the compositions defined above.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT

The composition of the invention can be formulated as a solution in a wide range of solvents. The solutions may contain from 0.01 to 99.9%; but more generally from about 5 to 30% by weight of the active composition. It is generally more convenient to provide the compositions in a water-diluted form: this may be accomplished by adding an emulsifier to the organic solution followed by dilution with water.

In general, the weight ratio of 2-methyl-3-isothiazolone to the second component in the composition may be in the range of from about 40:1 to about 1:32. The other specific and preferred ratios are given in the examples.

The synergism of two-component compositions is demonstrated by testing a wide range of concentrations and ratios of compounds, generated by two-fold serial dilutions in a Trypticase Soy Broth (TSB) growth medium of a microbicide in one dimension and another microbicide in the second dimension, against a bacterium Escherichia coli (ATCC 11229), or fungi Candida albicans (ATCC 11651), Aspergillus niger (ATCC 6275), or Aureobasidium pullulan (ATCC 9348). Each test tube was inoculated to make about 1-5×10⁷ bacteria per ml or 1-5×10⁵ fungi per ml. The lowest concentrations of each compound or mixtures to inhibit visible growth (turbidity) at 37° for E. coli and at 30° C. for the fungi for 7 days were taken as the minimum inhibitory concentration (MIC). The MIC were taken as end points of activity. End points for the mixtures of compound A (2-methyl-3-isothiazolone) and compound B (second component microbicide) were then compared with the end points for the isothiazolone A alone and compound B alone. Synergism was determined by a commonly used and accepted method described by Kull, F. C.; Eisman, P. C.; Sylwestrowicz, H. D. and Mayer, R. L., in applied Microbiology 9:538-541 (1961) using the ratio determined by

    Qa/QA+Qb/QB=Synergy Index (SI)

wherein

QA=concentration of compound A in parts per million (ppm), acting alone, which produced an end point;

Qa=concentration of compound A in ppm, in the mixture, which produced an end point;

QB=concentration of compound B in ppm, acting alone, which produced an end point;

Qb=concentration of compound B in ppm, in the mixture, which produced an end point.

When the sum of Qa/QA and Qb/QB is greater than one, antagonism is indicated. When the sum is equal to one, additivity is indicated, and when less than one, synergism is demonstrated.

The test results for demonstration of synergism of microbicide combinations are shown in Tables 1 to 7. Each table concerns the combination of 2-methyl-3-isothiazolone and one other microbicide, and shows:

1. the identity of the second microbicide (compound B);

2. test against E. coli, and C. albicans (C. alb);

3. the end-point activity in ppm measured by MIC for compound A alone (QA), for compound B alone (QB), for compound A in the mixture (Qa), or for compound B in the mixture (Qb);

4. the calculation of synergy index (SI) based on the formula SI=Qa/QA+Qb/QB, and the weight ratio of 2-methyl-3-isothiazolone (compound A) to compound B in the particular combination (A:B);

5. the range of weight ratios for synergism and the preferred weight ratios. It will be appreciated by those skilled in the art that the ratios given are approximate only.

The MIC values of each compound tested alone (QA or QB) are end-point activities.

                  TABLE 1                                                          ______________________________________                                         2-Methyl-3-isothiazolone (A)/p-Chloro-m-xylenol                                (B) Combination                                                                A           B         A:B    Synergy Index                                     ______________________________________                                         Tested in TSB with Escherichia coli                                            250 ppm     0 ppm                                                              125         62        2:1    0.75                                              62          125       1:2    0.75                                              31          125       1:4    0.62                                              16          125       1:8    0.56                                              8           125       1:16   0.53                                              4           125       1:32   0.52                                              0           250                                                                Tested in TSB with Candida albicans                                            250 ppm     0 ppm                                                              125         31        4:1    0.75                                              62          62        1:1    0.75                                              0           125                                                                ______________________________________                                          Range of ratios (A:B) is from 4:1 to 1:32                                

                  TABLE 2                                                          ______________________________________                                         2-Methyl-3-isothiazolone (A)/Sodium dichlorophene                              (B) Combination                                                                A           B         A:B    Synergy Index                                     ______________________________________                                         Tested in TSB with Escherichia coli                                            250 ppm     0 ppm                                                              125         16        8:1    0.62                                              125         31        4:1    0.75                                              62          31        2:1    0.50                                              31          31        1:1    0.37                                              16          31        1:2    0.31                                              16          62        1:4    0.56                                              8           62        1:8    0.53                                              4           62        1:16   0.52                                              0           125                                                                Tested in TSB with Candida albicans                                            250 ppm     0 ppm                                                              125         8         16:1   0.75                                              62          16        4:1    0.75                                              31          16        2:1    0.62                                              16          16        1:1    0.56                                              8           16        1:2    0.53                                              4           16        1:4    0.52                                              2           16        1:8    0.51                                              1           16        1:16   0.50                                              0           31                                                                 ______________________________________                                          Range of ratios (A:B) is from 16:1 to 1:16                               

                  TABLE 3                                                          ______________________________________                                         2-Methyl-3-isothiazolone (A)/Bis-(2-hydroxy-5-chlorophenyl)                    sulfide (B) Combination                                                        A           B         A:B    Synergy Index                                     ______________________________________                                         Tested in TSB with Escherichia coli                                            250 ppm     0 ppm                                                              125         16        8:1    0.62                                              125         31        4:1    0.75                                              62          62        1:1    0.75                                              31          62        1:2    0.62                                              16          62        1:4    0.56                                              8           62        1:8    0.53                                              0           125                                                                Tested in TSB with Candida albicans                                            250 ppm     0 ppm                                                              125         16        8:1    0.75                                              0           62                                                                 ______________________________________                                          Range of ratios (A:B) is from 8:1 to 1:8                                 

                  TABLE 4                                                          ______________________________________                                         2-Methyl-3-isothiazolone (A)/Benzylbromoacetate                                (B) Combination                                                                A           B         A:B    Synergy Index                                     ______________________________________                                         Tested in TSB with Escherichia coli                                            250 ppm     0 ppm                                                              125         6         20:1   0.53                                              125         12        10:1   0.56                                              125         25        5:1    0.62                                              62          25        2.5:1  0.37                                              62          50        1:2.1  0.50                                              31          50        1:1.5  0.37                                              31          100       1:3    0.62                                              16          100       1:6    0.56                                              8           100       1:12   0.53                                              0           200                                                                Tested in TSB with Candida albicans                                            250 ppm     0 ppm                                                              125         31                                                                 62          62        40:1   0.56                                              125         6         20:1   0.62                                              125         6         20:1   0.62                                              62          6         10:1   0.37                                              31          6         5:1    0.24                                              16          6         2.5:1  0.18                                              8           6         1.2:1  0.15                                              8           12        1:1.5  0.28                                              4           12        1:3    0.27                                              4           25        1:6    0.52                                              2           25        1:12   0.51                                              0           50                                                                 ______________________________________                                          Range of ratios (A:B) is form 40:1 to 1:12                               

                  TABLE 5                                                          ______________________________________                                         2-Methyl-3-isothiazolone (A)/Dodecylamine                                      (B) Combination                                                                A           B         A:B    Synergy Index                                     ______________________________________                                         Tested in TSB with Escherichia coli                                            125 ppm     0 ppm                                                              62          3         20:1   0.62                                              62          6         10:1   0.75                                              31          12        2.5:1  0.75                                              16          12        1.2:1  0.62                                              0           25                                                                 Tested in TSB with Candida albicans                                            250 ppm     0 ppm                                                              125         3         40:1   0.75                                              62          3         20:1   0.50                                              62          6         10:1   0.75                                              31          6         5:1    0.62                                              16          6         2.5:1  0.56                                              0           12                                                                 ______________________________________                                          Range of ratios (A:B) is from 40:1 to 1.2:1                              

                  TABLE 6                                                          ______________________________________                                         2-Methyl-3-isothiazolone (A)/4-(2-Nitrobutyl)morpholine                        (B) Combination                                                                A           B         A:B    Synergy Index                                     ______________________________________                                         Tested in TSB with Escherichia coli                                            125 ppm     0 ppm                                                              62          8         8:1    0.53                                              62          16        4:1    0.56                                              62          31        2:1    0.62                                              62          62        1:1    0.75                                              31          62        1:2    0.50                                              16          62        1:4    0.37                                              16          125       1:8    0:62                                              0           250                                                                Tested in TSB with Candida albicans                                            250 ppm     0 ppm                                                              125         8         16:1   0.56                                              125         16        8:1    0.62                                              125         31        4:1    0.75                                              62          31        2:1    0.50                                              31          31        1:1    0.37                                              31          62        1:2    0.62                                              16          62        1:4    0.56                                              8           62        1:8    0.53                                              4           62        1:16   0.52                                              0           125                                                                ______________________________________                                          Range of ratios (A:B) is from 16:1 to 1:16                               

                  TABLE 7                                                          ______________________________________                                         2-Methyl-3-isothiazolone (A)/Dipropylamine ether                               (B) Combination                                                                A           B         A:B    Synergy Index                                     ______________________________________                                         Tested in TSB with Escherichia coli                                            125 ppm     0 ppm                                                              62          6         10:1   0.56                                              62          12        5:1    0.62                                              62          25        2.5:1  0.75                                              31          50        1:1.6  0.75                                              0           100                                                                Tested in TSB with Candida albicans                                            250 ppm     0 ppm                                                              125         6         20:1   0.56                                              125         12        10:1   0.75                                              62          12        5:1    0.50                                              62          25        2.5:1  0.75                                              0           50                                                                 ______________________________________                                          Range of ratios (A:B) is from 20:1 to 1:1.6                              

The synergistic activities of the compositions of the invention in most cases are applicable to bacteria, fungi, and a mixture of bacteria and fungi. Thus, the combinations not only lower the use-level of biocide but also broaden the spectrum of activity. This is especially useful in situations where either component alone does not achieve the best results due to weak activity against certain organisms. 

What is claimed:
 1. A microbicidal composition consisting essentially of synergistic effective amounts of 2-methyl-3-isothiazolone and 4-(2-nitrobutyl)morpholine, wherein the ratio of 2-methyl-3-isothiazolone to 4-(2-nitrobutyl)morpholine is in the range of 40:1 to 1:32.
 2. The composition of claim 1, wherein the ratio of 2-methyl-3-isothiazolone to 4-(2-nitrobutyl)morpholine, is in the range of from about 16:1 to about 1:16.
 3. A microbicidal product containing from about 0.01 to about 99.9% by weight of the composition of claim 1, and an organic solvent.
 4. The microbiocidal product according to claim 3 containing from about 5 to about 30% by weight of the composition.
 5. The microbicidal product according to claim 3, further contains an emulsifier and water.
 6. A method for inhibiting the growth of a member selected from the group consisting of bacteria, fungi, algae and mixtures thereof in a locus subject to contamination by said member, which comprises incorporating onto or into the locus, in an amount effective to adversely affect the growth of said member, the composition of claim
 1. 7. The method of claim 6 wherein the locus is an aqueous medium, and the composition additionally contains an organic solvent, an emulsifier and water. 